linux-kernel - Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160123195920.552990ed@cotter.ozlabs.ibm.com>
Date:	Sat, 23 Jan 2016 19:59:20 +1100
From:	Balbir Singh <bsingharora@...il.com>
To:	Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	rjw@...ysocki.net, viresh.kumar@...aro.org,
	linux-pm@...r.kernel.org, pc@...ibm.com, anton@...ba.org,
	ego@...ux.vnet.ibm.com, shreyas@...ux.vnet.ibm.com
Subject: Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from
 hot-path

On Fri, 22 Jan 2016 12:49:02 +0530
Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com> wrote:

> cpu_to_chip_id() does a DT walk through to find out the chip id by
> taking a contended device tree lock. This adds an unnecessary overhead
> in a hot path. So instead of calling cpu_to_chip_id() everytime cache
> the chip ids for all cores in the array 'core_to_chip_map' and use it
> in the hotpath.
> 
> Reported-by: Anton Blanchard <anton@...ba.org>
> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
> Reviewed-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>

snip

Does the core_to_chip_map need to be updated/refreshed on/after/ a
cpu (core) hotplug? I presume id's don't change

Balbir